{"id":"CVE-2026-64567","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: reject free space cache with more entries than pages\n\nWhen loading a v1 free space cache, __load_free_space_cache() takes\nnum_entries and num_bitmaps straight fr…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: reject free space cache with more entries than pages\n\nWhen loading a v1 free space cache, __load_free_space_cache() takes\nnum_entries and num_bitmaps straight fr…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","published":"2026-08-05","updated":"2026-08-08","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64567","references":[{"url":"https://git.kernel.org/stable/c/33878ba25e2638bc0c61623d7a05c9ca2b74c039","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/5e1b2ca6b34939e70fb0785e8222b53cf060016f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a2d8d5647ed854e38f941741aea45b9eb15a6350","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f9fef131fa3f59b857217f522fa5ea430d1b707c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8ded74c654a982dc8581a17b0caa7fcedb20de69"},{"url":"https://git.kernel.org/stable/c/c9c38066b6446e83668c041702bb639b0ca49363"},{"url":"https://git.kernel.org/stable/c/094734c7aaa2b36751dc32480a680a4952685e78"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64567.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-64567"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2511408"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-64567"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64567"},{"url":"https://lore.kernel.org/linux-cve-announce/2026080558-CVE-2026-64567-a7b8@gregkh/T"}],"tags":["nvd","cve.org","csaf","vex","red-hat","score-dispute"],"epss":0.00125,"epssPercentile":0.02178,"ingestedAt":"2026-08-08T20:29:49.170Z","vendor":"Linux","product":"Linux","affected":["Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < 8ded74c654a982dc8581a17b0caa7fcedb20de69","Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < c9c38066b6446e83668c041702bb639b0ca49363","Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < 094734c7aaa2b36751dc32480a680a4952685e78","Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < 33878ba25e2638bc0c61623d7a05c9ca2b74c039","Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < 404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2","Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < 5e1b2ca6b34939e70fb0785e8222b53cf060016f","Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < f9fef131fa3f59b857217f522fa5ea430d1b707c","Linux >= 5b0e95bf607ddd59b39f52d3d55e6581c817b530 < a2d8d5647ed854e38f941741aea45b9eb15a6350","Linux 3.2"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:42:59.944567Z"},"cwe":["CWE-125"],"scores":{"nvd":7.8,"vendor":5.5,"cna":7.8},"slug":"CVE-2026-64567","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: reject free space cache with more entries than pages\n\nWhen loading a v1 free space cache, __load_free_space_cache() takes\nnum_entries and num_bitmaps straight from the on-disk\nbtrfs_free_space_header. That header is stored in the tree_root under a key\nwith type 0, which the tree-checker has no case for, so neither count is\nvalidated before the load trusts it.\n\nThe load loops num_entries times and maps the next page whenever the current\none runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which\ndoes io_ctl->pages[io_ctl->index++]. But pages[] is allocated in\nio_ctl_init() from the cache inode's i_size, not from num_entries:\n\n\tnum_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);\n\tio_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);\n\nSo if num_entries claims more records than the pages can hold, io_ctl->index\nruns off the end of pages[]. The write side never hits this because\nio_ctl_add_entry() and io_ctl_add_bitmap() both stop once\nio_ctl->index >= io_ctl->num_pages; the read side just never had the same\ncheck.\n\nTo trigger it, take a clean cache (num_entries = <N> here), set num_entries\nin the header to 0x10000, and fix up the leaf checksum so it still passes\nthe tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and\npages[] is a 16-pointer (kmalloc-128) array. The load now tries to read\n65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the\narray:\n\n  BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\n  Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58\n   io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\n   __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820)\n   load_free_space_cache (fs/btrfs/free-space-cache.c:1017)\n   caching_thread (fs/btrfs/block-group.c:880)\n   btrfs_work_helper (fs/btrfs/async-thread.c:312)\n   process_one_work\n   worker_thread\n   kthread\n   ret_from_fork\n\nfree-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc()\nat line 565, which is why that is the frame KASAN names. The out-of-bounds\nslot is then treated as a struct page and handed to crc32c(), so the bad\nread turns into a GP fault.\n\nAdd the missing check to io_ctl_check_crc(), which is where both the entry\nloop and the bitmap loop end up. When num_entries is too large the load now\nfails like any corrupt cache: __load_free_space_cache() drops it and rebuilds\nthe free space from the extent tree, so a valid cache is never rejected.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64567.json)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}